Up to 85% of people have a vestigial muscle called the " palmaris longus."

多达85％有一种叫做“掌长肌”退化肌肉。

Looking at our primate relatives, we can see that the palmaris longus is sometimes absent in those that spend more time on the land, but always present in those that spend more time in trees.

观察一下我们灵长类先，我们可以发现，那些在陆地上生活更久有时没有掌长肌，但是，那些在树上生活更久总是有掌长肌。